Abstract
Purpose :
To evaluate flow rates in water and vitreous for various gauges single and dual cutting action guillotine style vitrectors across their operational range of the cut rate and vacuum
Methods :
Three gauges of guillotine style cutters with single (S23 and S25) and dual (D23, D25 and D27) cutting action were evaluated in the laboratory setting driven by the same venturi-based system. The study focused on obtaining flow data under two test conditions, water and vitreous harvested from pig eyes. For water flow testing, each cutter sample was run three times (1 min each) at 0, 500, 1.5K, 2.5K, 5K, 7.5K cut/min rates; for vitreous - one sample was run at the same cut rates. All cutters were tested at the same two vacuum levels (300 & 600 mmHg). Flow rates were calculated based on the extracted medium weight differential and the run time recorded by a stop watch
Results :
The average water flow rates (AWFR) for S23 vs D23 with vacuum of 600mmHg were 10.48 vs 27.13 at 7.5K and 25.17 vs 27.05 g/min at 0 cpm; with 300mmHg - 4.13 vs 16.20 and 15.46 vs 16.45 g/min at 7.5K and 0 cpm respectively. AWFR for S25 vs D25 with vacuum of 600mmHg - 5.87 vs 14.29 at 7.5K and 14.63 vs 14.31 g/min at 0 cpm; with 300mmHg at 7.5K and 0 cpm were 3.16 vs 8.47 and 8.52 vs 8.42 g/min respectively. AWFR for D27 was 5.86 at 7.5K and 5.83 g/min at 0 cpm with 600 mmHg vacuum; for 300 mmHg vacuum at 7.5K and 0 cpm were 3.33 and 3.25 g/min, respectively. The average vitreous flow rates (AVFR) for S23 vs D23 were 2.21 vs 5.93 at 7.5K and 1.67 vs 2.67 g/min at 500 cpm with 600 mmHg vacuum and 1.10 vs 1.82 at 7.5K and equal 0.27 g/min at 500 cpm with 300 mmHg vacuum. AVFR for S25 vs D25 with 600 mmHg vacuum were 1.46 vs 2.88 at 7.5K and 0.67 vs 0.87 g/min at 500 cpm, with 300mmHg vacuum 0.75 vs 1.50 at 7.5K and 0.21 vs 0.37 g/min at 500 cpm. AVFR for D27 were 1.32 vs 0.42 g/min at 7.5K and 500 cpm respectively with vacuum at 600mmHg, and with 300mmHg vacuum - 0.68 at 7.5K vs 0.10 g/min at 500 cpm
Conclusions :
The water data shows that Dual cutters “always open port” design does not suffer from duty-cycle related reduction in AWFR with increasing cut rate. Cutters of the same gauge with higher AWFR at 0 cpm tend to also have higher AVFR at low speeds; although at higher speeds, the advantage may be overcome by a Dual style cutter when compared to a high performing open water flow Single cutter
This is a 2020 ARVO Annual Meeting abstract.